1. Technical Field
The present invention relates, for example, to a circuit device, a transmission module, an electronic apparatus, and a moving object.
2. Related Art
There is a known RF transmitter that outputs a transmission signal in an RF band, such as an automobile keyless entry module (key side). In an apparatus of this type, a communication circuit device (semiconductor integrated circuit or IC, for example) is controlled by a control IC (controller, microcomputer) to generate and output the transmission signal.
For example, JP-2006-261714 discloses a circuit device having an interface with a control IC (baseband IC), uses a fractional-N-type PLL circuit (PLL circuit having sigma-delta modulator) to generate a carrier wave signal, and uses a power amplifier to drive an antenna for wireless communication.
The circuit device receives the following two pieces of information from the controller: information for setting the frequency of the carrier wave, a modulation method, and other factors (transmission action setting information); and transmission data to be actually transmitted on a transmission signal in an RF band. Since a desired transmission signal cannot be generated without the transmission action setting information, it is required to receive the transmission action setting information at highest possible speed at timing before transmission starts. On the other hand, the transmission data communication speed is restricted by an implemented apparatus that receives the transmission signal (a receiver in an automobile in the case of a keyless entry module), and a communication speed of about several kHz typically suffices. That is, a plurality of pieces of information are transmitted and received to and from the circuit device and the controller at different desirable transmission speeds.
In JP-2006-261714, the communication between the controller and the circuit device is performed by three-line serial communication, and action setting communication (communication of transmission action setting information) and RF transmission data communication (communication of transmission data), which are desirably performed at different transmission speeds, are performed by single serial communication. The communication therefore needs to be performed in accordance with the transmission rate in the slow communication, resulting in inefficient communication.